1. Field of the Invention
The present invention relates to a washing machine, and more particularly to a method of controlling a multi-tub washing machine, which controls washing procedures of one washing tub in consideration of washing procedures of the other washing tub while driving at least two washing tubs simultaneously.
2. Description of the Related Art
In general, a drum type washing machine washes laundry in a washing tub by performing an operating command, which may call for one or more processes, e.g., washing, rinsing and dehydrating processes. A recently developed washing machine is equipped with a drying device for drying dehydrated laundry. But since a conventional washing machine includes one washing tub, a user should sort the laundry according to a kind or dyeing of cloth, and put a first sorted group of laundry, which can be washed together, into the washing tub. After the washing of the group of laundry is completed, the user has to put another sorted group of laundry that can be washed together into the washing tub. Since, in this case, the washing machine will be operated twice or more, it is highly time and energy consumptive. Further, if a relatively small volume of laundry is washed by a large capacity washing machine, power consumption is increased unnecessarily.
To solve the above problems, a twin-tub washing machine for performing an independent washing operation in each tub has been developed, and is disclosed in Korean Patent Laid-open Publication No. 10-2004-0009400. Such a washing machine has a large capacity washing tub and a small capacity washing tub, which are driven individually or simultaneously.
But when the large capacity and small capacity washing tubs are driven simultaneously, the washing operations (i.e., water supplying, washing, rinsing, dehydrating and drying processes) of one washing tub affects the washing operations of the other washing tub. In more detail, when the water supplying process or the draining process is performed in two washing tubs simultaneously, the water may be supplied insufficiently in the washing tubs or discharged incompletely from the washing tubs. When the dehydrating process is performed in two washing tubs simultaneously, noise may be generated due to resonance and the washing machine may even break. When the water heating process or the drying process is performed in two washing tubs simultaneously, or when the water heating process and the drying process are performed together, a current overload may happen because of the simultaneous operations of heaters for heating the water and/or heaters for drying the washed laundry.
A twin-tub washing machine for solving one of the above problems (simultaneous water supplying or draining) is disclosed in Japanese Patent Laid-open Publication No. H10-15276. Such a washing machine is constructed such that a single water supply pipe and a single drain pipe is connected to two washing tubs. While the water supplying process or draining process is performed in one washing tub, the water supplying or draining in the other washing tub is prohibited and delayed.
But just to delay the water supplying or draining cannot ensure that the water is supplied sufficiently into both the washing tubs or discharged completely from both the washing tubs. Further, such a washing machine cannot solve the above-noted problems that arise during simultaneous dehydrating or drying.